Semiconductor devices, such as field effect transistors (FETs), are the core building block of a vast majority of electronic devices. A FET includes a channel between source and drain regions, where an electrical current can flow through the channel. A metal-semiconductor field effect transistor (MESFET) uses a Schottky junction to control the resistance of the channel to current flow from the source to the drain. MESFETs are typically constructed with substrates that lack high quality surface passivation, such as gallium arsenide. MESFETs tend to be faster than metal oxide semiconductor field effect transistors (MOSFETs), but they also tend to be more expensive. MOSFETs utilize a gate insulator and a gate positioned over the channel to apply a bias to the channel and thereby control the resistance of the channel. MESFETs are useful in radio frequency applications, such as for switch and/or amplifier purposes, in part due to the higher electron mobility and lower capacitance of a MESFET compared to a MOSFET.
The materials used for MESFETs tend to be more expensive, and the materials limit scalability and higher level integration because most semiconductor devices utilize a silicon-based substrate. Junction gate field effect transistors (JFETs) are similar to a MESFET, where a JFET uses a p-n junction for the gate. In a JFET, a highly conductive material such as a metal serves as the gate terminal and directly contacts the semiconductive material of the channel (as opposed to a MOSFET where a gate insulator physically separates the channel from the electrically conductive gate.) JFETs are exclusively voltage controlled, and do not need a biasing current. A reverse bias voltage applied to the gate terminal “pinches” the channel and increases the electrical resistance between the source and drain. JFETs have been reported as having higher lateral breakdown voltage than MOSFETS, and many JFETs can operate at higher ambient temperatures, such as about 200 degrees centigrade (° C.). JFETs also tend to have higher gain and lower flicker noise than MOSFETs. Because JFETs do not include the gate insulator used in MOSFETs, JFETs avoid defects that may occur in the gate insulator of MOSFETs.
The semiconductor industry is continuously moving toward the fabrication of smaller and more complex microelectronic components with higher performance. The production of smaller integrated circuits requires the development of smaller electronic components, and closer spacing of those electronic components within the integrated circuits. The source and drain in a MOSFET are typically closer together than in a JFET, so the use of JFETs tends to increase the size of integrated circuits. In typical JFET manufacturing processes, silicide blocks are used to separate the source and the drain from the channel. The silicide block has a relatively large margin of error, and produces a relatively large gate to source (or gate to drain) distance, such as about 0.4 nanometers or more.
Accordingly, it is desirable to provide integrated circuits with JFETs and methods of producing the same. In addition, it is desirable to provide integrated circuits with JFETs having smaller dimensions, such as gate to source or gate to drain distances of about 0.4 nanometers or less. Furthermore, other desirable features and characteristics will become apparent from the subsequent detailed description and the appended claims, taken in conjunction with the accompanying drawings and this background.